Need help on what I'm doing wrong/ what to improve on

https://www.chess.com/blog/KeSetoKaiba/opening-principles-again
I am really liking this resource. It is a cool way to share information without having to re-type explanations like I used to do
Play slower time controls a lot. When I was a beginner I play atleast one 45 min or 1 hr time control games almost every day. I did not know what and where to find good chess tactics and endgame books. So I tried to familiarize openings on what programs Chessmaster and Fritz played and I tried to play them myself instead. Beginners today are very lucky. Access to information are now very easy.
The best advice I can give you is "Accept that your opponent is in your head and can see exactly what you plan on doing". Another thing you can do is when it is your turn to play, look for your opponents best move first before thinking about the best move you can do.